none that I've seen so far, except maybe a little low-light focus hunting

I've had this lens for about 3 months and have taken some of my best pictures with it. I have a canon 10-22 EF-S lens and this lens has better color and contrast than that one - and edges it out in sharpness as well. This lens is on my camera 80% of the time and I can always count on it to deliver crisp, clean images throughout the focal range.

The footer on this lens says that its a "macro" and I think it's mininum focusing distance is pretty good, as well as its sharpness for closeups - but the working focal length (between the subject and the front of the lens) is pretty small, so keep that in mind. The bokeh on this lens, however, is very pleasing and the f/2.8 makes for a pleasantly small DOF for closeup photos.

I've not used the canon 24-70L yet, but if it beats out this lens it must be a pretty darned good lens.